From Longman Dictionary of Contemporary Englishspill your gutsspill your gutsAmerican English informalADMIT to tell someone all about your private life, or about a personal secret → spill
Examples from the Corpus
spill your guts• Rob let Al talk until he finally spilled his guts about his affair with Louise.• Albert let Rob run on till he spilled his guts, but Loulse probed. 